Tuesday night, while Bush did not mention Trump, he rejected any style of leadership that involves "pushing other people down to make yourself feel better." True leadership involves "forging consensus and having a servant's heart," as well as exhibiting integrity and backbone, he said.

Bush called for immigration reform that supports economic goals, not just the reunification of extended families. He spoke up for a path to legal residency for so-called "dreamers," undocumented immigrants who arrived in American as children and who are pursuing educational and work opportunities.

Most Republicans make a distinction between undocumented immigrants who commit crimes, and those who are "working hard, trying to make ends meet," Bush said.

He responded to audience questions about voter suppression, the death penalty, criminal justice reform, and affirmative action, and repeatedly returned to the themes of optimism, prosperity, and compromise.

"We need to re-energize the compromise gene; the consensus muscle," he said. "Find common ground on the smallest thing and build on it."

There are two ways to make a chimera. The first is to introduce the organs of one animal into another—a risky proposition, because the host’s immune system may cause the organ to be rejected.

The other method is to begin at the embryonic level, introducing one animal’s cells into the embryo of another and letting them grow together into a hybrid.

It sounds weird, but it’s an ingenious way to eventually solve a number of vexing biological problems with lab-grown organs.

When scientists discovered stem cells, the master cells that can produce any kind of body tissue, they seemed to contain infinite scientific promise. But convincing those cells to grow into the right kinds of tissues and organs is difficult.

Cells must survive in Petri dishes. Scientists have to use scaffolds to make sure the organs grow into the right shapes. And often, patients must undergo painful and invasive procedures to harvest the tissues needed to kick off the process.

>President of the European Council Tusk, President of the European Commission Juncker, and the Maltese Prime Minister Muscat, want to shut down the Libyan migration route within the next couple of months. If this does not happen soon, then Marine le Pen and Geert Wilders - supported by millions of dissatisfied civilians - will destroy the EU from within, Muscat warns.

>Because of the urgency of this problem, President of the European Council Tusk may even consider drastic measures that were off limits until recently, such as locking down the Libya coast. Tusk calls such a solution 'raising a defensive wall' in a confidential report to the EU states that he wrote together with Muscat. This afternoon, the European Commission will present a series of measures that underline the urgency: "before spring and summer roll around, decisive action will be required".